Resource Science: Environmental impact statements and population growth

Many people in farming, ranching, oil and gas, timber and mining know about Environmental Impact Statements (EIS) required under the National Environmental Policy Act (NEPA). An EIS is an assessment of the impacts of any project that’s considered a major federal action that significantly affects the environment. In agriculture, NEPA can apply with federal grazing leases, timber sales, permits and other activities with a federal government connection. A large industry has developed around doing EIS including lawyers, consultants, economists, scientists, engineers, government agencies and environmental groups.

I’ve worked on EIS, and they can be very hard and complicated to write. One of the topics in an EIS is cumulative impacts (also called cumulative effects). The Council on Environmental Quality describes cumulative effects as the impact on the environment which results from the incremental impact of the action when added to other past, present and reasonably foreseeable future actions. In other words, the impacts of a proposed project combined with all other actions.

For example, if an EIS is assessing the effects of a grazing lease on a wildlife population, an EIS must also consider the effects of nearby logging, mining or other human activities. It’s not a simple process. EIS can now also consider the cumulative effects of climate change along with a project’s direct impacts on the environment. That can get really complicated.

If EIS can consider climate change, which is a worldwide issue, what about human population growth, which is the root cause of human-caused environmental impacts? For example, more people can result in more greenhouse gases and more road traffic with more roadkill of wildlife. Maybe human population growth should be considered in EIS.

The U.S. population is growing with associated environmental impacts as I’ve written about before (WLJ July 11, 2025, and Nov. 8, 2024). The Census Bureau reports that the U.S. population has grown from 76 million people in 1900 to 342.5 million people as of Sept. 11 (see the graph below). There has been an increase of almost half a million (464,506) people in the period from June 25 to Sept. 11. There is now one birth every eight seconds, one death every 11 seconds, one international migrant every 22 seconds and a net gain of one person every 14 seconds.

Immigration contributes to the U.S. population growth. One immigrant per 22 seconds equals about three people per minute, 164 per hour, 3,927 per day, 1,433,454 per year and 14,334,545 per decade. The Department of Homeland Security (DHS) also keeps data on immigration and reports there were about 1.6 million legal immigrants per year from 2022 to 2023. This is close to the 1.4 million immigrants per year calculated from the Census Bureau data, which suggests that the Census Bureau is reporting legal, and not illegal, immigrants.

The DHS data are somewhat complicated, but as far as I can tell, there were 2,310,000 illegal (called unauthorized by DHS) immigrants in 2022 (see the references below). If there are about 1.5 million legal immigrants and 2.3 million illegal immigrants per year, then immigration adds about 3.8 million people to the U.S. population each year. This rate of immigration will not be the same each year, and not all immigrants will stay in the U.S. permanently, but immigration does increase the population substantially. The U.S. Law Guide noted that “reports indicate that immigration was the primary driver of the nation’s population growth between 2022 and 2023.”

If an EIS considered population growth as a cumulative effect, it would bring attention to the contribution of immigration, legal and illegal, to population growth. An increasing population is good for growth of the economy and markets, so its impacts are not necessarily negative.

However, from an environmental standpoint, increasing numbers of people will increase human impacts. Considering the effects of population growth might put into perspective the comparatively small impacts of grazing, farming and timber harvest. Environmental groups that emphasize every possible negative impact of agriculture and resource development should recognize this.

The positive and negative aspects of population growth, and immigration’s effect on it, are to a large extent, a matter of personal opinion. I suppose a balance of the effects of population growth on economics and the environment is needed. Immigration is the one population factor that the government can control to achieve such a balance. Regardless, it seems reasonable to include population growth in an EIS if all cumulative environmental impacts are to be considered. It’s at least as relevant as including climate change in EIS assessments of cumulative impacts. — Matt Cronin, WLJ columnist 

(Matt Cronin is a biologist with Northwest Biology and Forestry Company LLC in Bozeman, MT, and a teaching professor at Montana State University. He may be contacted at croninm@aol.com.)